cgl: add make_current_surfaceless

This follows the EGL api to make surfaceless platforms.

CHANGELOG.md

@@ -1,6 +1,7 @@
 # Unreleased
 
 - Add `PossiblyCurrentContext::make_not_current_in_place(&self)` for when `Send` capability of `NotCurrentContext` is not required.
+- Add `NotCurrentContext::make_current_surfaceless(self)` and `PossiblyCurrentContext::make_current_surfaceless(&self)` in the `Cgl` implementation to allow the use of surfaceless contexts on MacOS.
 
 # Version 0.32.1
 

glutin/src/api/cgl/context.rs

@@ -74,6 +74,13 @@ pub struct NotCurrentContext {
 }
 
 impl NotCurrentContext {
+    /// Make a [`Self::PossiblyCurrentContext`] indicating that the context
+    /// could be current on the thread.
+    pub fn make_current_surfaceless(self) -> Result<PossiblyCurrentContext> {
+        self.inner.make_current_surfaceless()?;
+        Ok(PossiblyCurrentContext { inner: self.inner, _nosendsync: PhantomData })
+    }
+
     fn new(inner: ContextInner) -> Self {
         Self { inner, _nosync: PhantomData }
     }
@@ -143,6 +150,13 @@ pub struct PossiblyCurrentContext {
     _nosendsync: PhantomData<*mut ()>,
 }
 
+impl PossiblyCurrentContext {
+    /// Make this context current on the calling thread.
+    pub fn make_current_surfaceless(&self) -> Result<()> {
+        self.inner.make_current_surfaceless()
+    }
+}
+
 impl PossiblyCurrentGlContext for PossiblyCurrentContext {
     type NotCurrentContext = NotCurrentContext;
     type Surface<T: SurfaceTypeTrait> = Surface<T>;
@@ -236,6 +250,19 @@ impl ContextInner {
         })
     }
 
+    fn make_current_surfaceless(&self) -> Result<()> {
+        autoreleasepool(|_| {
+            self.update();
+            self.raw.makeCurrentContext();
+
+            run_on_main(|_mtm| unsafe {
+                self.raw.setView(None);
+            });
+
+            Ok(())
+        })
+    }
+
     fn context_api(&self) -> ContextApi {
         ContextApi::OpenGl(None)
     }